1. Field of the Invention
The present invention pertains to a method that dynamically adjusts the rotational speed of a motor of a disk drive according to the data transfer rate from the computer system and the data error rate while reading data.
2. Description of the Prior Art
The increase in the operating speed of personal computers (PCs) has been accompanied by improvements in the transfer speed and capacity of peripheral devices. Under these circumstances, computer storage media have also become multifunctional, instead of simply functioning as a means for the storage of information. For example, the contents of a CD-ROM disk can be music, data, or video. However, different applications may have large differences in the transfer rate between the optical disk drive and the PC. For example, when a VCD movie is playing, the transfer rate is only 176 Kbyte/sec, that is, the so-called unit speed. On the other hand, the transfer rate of a document file can exceed 10 Mbyte/sec, an order of magnitudes.
In order to ensure that motor-driven disk drives, such as for CD-ROMs, magnetic disks, or hard disks, can provide the transfer rate required by the computer, the motor is usually set to a rotational speed that is much higher than necessary. Thus, in conventional disk drives, it is very common for the motor to rotate the disk at a very high speed even when the transfer rate required by the computer is fairly low. This results not only in inefficient power consumption, but also in noise, vibration, and degradation in reading quality when the motor rotates at high speeds. In addition, reading data at too high a speed may also result in the deterioration in performance of the disk drive.
Therefore, as described above, conventional high-speed disk drives typically read data from disks at a set (i.e., fixed) and relatively high rotational speed. Regarding the setting of the motor speed of the disk drive, the difficulty is how to calculate the transfer rate required by the computer system. Since the transfer rate between the computer system and the disk drive is affected by the time that the disk drive itself spends reading data, one cannot simply assume that the amount of data transferred per unit time is the transfer rate.